Orbiter - Stellarium equinox difference

[mstram]

I set the MJD to 55640.972917 (March 20 23:21 -- 2011)

With the DG positioned at -79.648 43.678 and pointed due west (270) the sun is directly ahead and positioned on the horizon.

With the same date entered in Stellarium, the Sun is shown at Az/Alt = +337deg 30' 50" / -44 00 06

If I set the time in Stellarium to 18:05 it matches up with Orbiter

Why the difference ?

 

[n72.75]

Stellarium is obviously wrong.

 

[Stoat]

It's probably down to the wonders of the Julian calendar, and the start of the day being midday, shifted to midnight for convenience. That's my guess at any rate.

Where lots of people come acroppa with astronomical dating, is with those extra days added into the calendar.Try shifting the date by 11 days forward.

 

[kuddel]

Hi there,

...are you sure Stellarium uses MJD? I think it uses just JD...
those two are 12 hours apart.

/kuddel

 

[martins]

I set the MJD to 55640.972917 (March 20 23:21 -- 2011)

With the DG positioned at -79.648 43.678 and pointed due west (270) the sun is directly ahead and positioned on the horizon.

With the same date entered in Stellarium, the Sun is shown at Az/Alt = +337deg 30' 50" / -44 00 06

If I set the time in Stellarium to 18:05 it matches up with Orbiter

Why the difference ?

The fact that the difference is about 5.25 hours and that your position is about 5.3 hours west of Long=0 seems suspicious. Are you sure you didn't use a local time parameter in stellarium?

 

[Stoat]

I think I've sussed it. In stellarium, go to the location box and type Tampa into the search. That puts you in Florida. Then change it slightly to your coordinates. I think you may have transposed long and lat, or w and e.

 

[mstram]

As Emily used to say "Never mind"

 

[orb]

I just looked in the manual, and it defaults to the p.c. date /time.

So what time / date system is that ?

I just used the interface's date time thing .. dunno what time system it's using.

It seems from the manual that it's just "local" time.. it also mentions time zones.

What is your guess about the ~5 hour difference ?

Your timezone (set for forum) is UTC-5, so probably your PC's clock is UTC-5 too. This would give 5 hours difference to UTC time, which is used in Orbiter.

 

[Stoat]

I tried it in Stellarium, at Toronto and it's okay. There has to be something awry with your copy of Stellarium.

 

[mstram]

Your timezone (set for forum) is UTC-5, so probably your PC's clock is UTC-5 too. This would give 5 hours difference to UTC time, which is used in Orbiter.

Ah !

That's what it is.

I didn't notice that Orbiter is using UTC

Thx to all for your replies

---------- Post added at 02:24 PM ---------- Previous post was at 02:21 PM ----------

I tried it in Stellarium, at Toronto and it's okay. There has to be something awry with your copy of Stellarium.

No, there's something wrong with my brain